There is a need for an environmentally degradable disposable material as a potential replacement for the tremendous amount of conventional plastic materials which, when discarded, do not degrade well. Approximately 60.5 billion pounds of plastic polymers were produced in the United States in 1991, of which approximately 15 billion pounds were one-way, or non-returnable, plastics used in packaging. A significant amount of these plastic materials are discarded and become pollutants that deface the landscape and threaten marine life. At least about one million seabirds and about 100,000 marine mammals die each year as the result of plastic pollutants.
A further problem with the disposal of nondegradable plastics is the concern for dwindling landfill space. It has been estimated that most major cities will have used up available landfills for solid waste disposal during the 1990's. Plastics currently comprise approximately 8 percent of the weight of and about 17 percent of the volume of solid waste.
However, there are good reasons for the use of plastics as, for example, packaging materials. Plastics provide appealing aesthetic qualities in the form of attractive packages which can be quickly fabricated and filled with specified units of products. The packages maintain cleanliness, storage stability, and other desirable qualities such as transparency. Packages made of conventional plastics are known for their low cost of production and chemical stability. This stability, however, leads to the discarded packages remaining in the environment for long periods of time, typically on the order of tens to hundreds of years.
A number of biodegradable polymers have been described, including polymers of some hydroxycarboxylic acids, such as lactic acid, which are attractive because of their biocompatible and thermoplastic nature. Polymers of hydroxycarboxylic acids can be degraded into monomers and small oligomers over time by hydrolysis under most environmental conditions. The resulting monomers and small oligomers are then readily taken up by organisms in the environment and can be aerobically converted to carbon dioxide and water or anaerobically converted to carbon dioxide and methane. Polymers of hydroxycarboxylic acids can also be degraded in the bodies of humans and other animals, a property which has led to the well-documented use of such polymers in the biomedical field as, for example, sutures, implants, and drug delivery devices.
However, the inventors are unaware of anyone having developed or commercialized technology to control the degradation of biodegradable disposable materials in a manner to render such materials useful. That is, a suitable disposable material should be stable throughout its useful life, which spans from when the material was produced through storage and use stages, but should be susceptible to rapid degradation upon disposal. The Kirk-Othmer Encyclopedia of Chemical Technology, 3rd edition, Supplement Volume, Alcohol Fuels to Toxicology, p. 647, 1984, predicts that biodegradable packages are "unlikely to be developed except in very special situations" because biodegradable packages are expensive, deficient in "required" properties, and more difficult to recycle. This article also states that blends of biodegradable polymers with the nondegradable polymers polyethylene, polystyrene, polypropylene, or polyethylene terephthalate are still not biodegradable. Encyclopedia '92, Modern Plastics mid-October 1991 issue, vol. 68, p. 163, also discourages the use of biodegradable polymers, stating that natural polymers "are not yet in large-scale production and are very expensive."
Therefore, a need exists for a cost-effective environmentally degradable disposable material with appropriate properties and desired degradation characteristics.